MEMS optical latching switch

ABSTRACT

An optical micro-electro-mechanical system (MEMS) switch is disclosed. In a preferred embodiment the optical MEMS switch is used as an M×N optical signal switching system. The optical MEMS switch comprises a plurality of optical waveguides formed on a cantilever beam platform for switching optical states wherein the state of the optical switch is changed by a system of drive and latch actuators. The optical MEMS device utilizes a latching mechanism in association with a thermal drive actuator for aligning the cantilever beam platform. In use the optical MEMS device may be integrated with other optical components to form planar light circuits (PLCs). When switches and PLCs are integrated together on a silicon chip, compact higher functionality devices, such as Reconfigurable Optical Add-Drop Multiplexers (ROADMs), may be fabricated.

This application claims the benefit of Provisional Patent ApplicationNo. 60/456,063, filed Mar. 19, 2003.

CROSS-REFERENCE TO RELATED APPLICATIONS

Attention is directed to copending provisional applications U.S.Provisional Application No. 60/456,086, filed Mar. 19, 2003, entitled,“M×N Cantilever Beam Optical Waveguide Switch” and U.S. ProvisionalApplication No. 60/456,087, filed Mar. 19, 2003, entitled, “MEMSWaveguide Shuttle Optical Latching Switch”. The disclosure of each ofthese copending provisional applications are hereby incorporated byreference in their entirety.

BACKGROUND

This invention in embodiments relates to microelectromechanical system(MEMS) switches and more particularly to multiple state optical latchingswitches.

The telecommunications industry is undergoing dramatic changes withincreased competition, relentless bandwidth demand, and a migrationtoward a more data-centric network architecture. First generationpoint-to-point wave division multiplex systems have eased the trafficbottleneck in the backbone portion of a network. As a new cross-connectarchitecture moves the technology closer to the subscriber side of thenetwork, operators are challenged to provide services at the opticallayer, calling for more flexible networks that can switch and reroutewavelengths. This is placing great emphasis and demand for wavelengthagile devices.

The need to provide services “just in time” by allocation ofwavelengths, and further migration of the optical layer from thehigh-capacity backbone portion to the local loop, is driving thetransformation of the network toward an all optical network in whichbasic network requirements will be performed in the optical layer.

The optical network is a natural evolution of point-to-point densewavelength division multiplexing (DWDM) transport to a more dynamic,flexible, and intelligent networking architecture to improve servicedelivery time. The main element of the optical network is the wavelength(channel), which will be provisioned, configured, routed, and managed inthe optical domain. Intelligent optical networking will be firstdeployed as an “opaque” network in which periodic optical-electricalconversion will be required to monitor and isolate signal impairments.Longer range, the optical network will evolve to a “transparent” opticalnetwork in which a signal is transported from its source to adestination totally within the optical domain.

A key element of the emerging optical network is an optical add/dropmultiplexer (OADM). An OADM will drop or add specific wavelengthchannels without affecting the through channels. Fixed OADMs cansimplify the network and readily allow cost-effective DWDM migrationfrom simple point-to-point topologies to fixed multi-pointconfigurations. True dynamic OADM, in which reconfiguration is done inthe optical domain without optical-electrical conversion, would allowdynamically reconfigurable, multi-point DWDM optical networks. Thisdynamically reconfigurable multi-point architecture is slated to be thenext major phase in network evolution, with true OADM an enablingnetwork element for this architecture.

On chip integration of optical switching and planar light circuits hasthe potential to greatly reduce the size and manufacturing costs ofmulti-component optical equipment such as Reconfigurable OpticalAdd/Drop Multiplexers (ROADMs). Current costs for Reconfigurable OpticalAdd/Drop Multiplexers (ROADMs) are $1,000 per channel, limiting theiruse to long-haul optical telecommunications networks. In order to extendtheir use into the metropolitan network the cost will need to bedecreased by an order of magnitude to $100 per channel, withoutsacrificing performance.

One solution to decreasing cost is through the integration ofcomponents, where the primary cost savings will be in packaging. Anumber of approaches are being pursued for optical integration usingPlanar Light Circuit (PLC) technologies. The majority of approaches usea silica-on-silicon platform with the ROADM formed from the integrationof silica Arrayed Waveguide Gratings (AWG's) for multiplexing anddemultiplexing, with Thermo-Optic (TO) switches for performing theadd/drop and pass of the demultiplexed signal. The use of a low-indexcontrast silica-on-silicon platform severely limits the yield of thesecomponents due to the requirement for uniform thick oxide films overlarge areas to form the waveguides. The use of TO switches limits theextensibility due to high-power requirements and thermal cross-talk.

A number of different materials and switching technologies are beingexplored for fabricating chip-scale photonic lightwave circuits such asAWG's for demultiplexers and multiplexers, Variable Optical Attenuators(VOA's) and Reconfigurable Optical Add-Drop Multiplexers (ROADMs). Themain material platforms include silica wafers, silica-on-siliconsubstrates using both thin film deposition and wafer bonding techniques,polymer waveguides defined on silicon substrates, andsilicon-on-insulator substrates. The main switching technologies includeMach-Zehnder interferometers based on either a thermo-optic orelectro-optic effect, and MEMS mechanical waveguide switches.

While silica waveguides have optical properties that are well matched tothe optical properties of conventional single mode fibers, and thuscouple well to them, they require thick cladding layers due to the lowindex of refraction contrast between the waveguide core and claddingmaterials, making them difficult to fabricate using planar processingtechniques for fabrication and integration with other on-chip opticaldevices. The low index of refraction contrast, Δn, between core andcladding also requires large bending radii to limit optical loss duringpropagation through the photonic lightwave circuit, leading to largechip footprints and low die yields (<50%).

In addition, silica based waveguide switches are typically based onMach-Zehnder interference using thermo-optic effects, that have alimited Extinction Ratio (ER) of around 25-30 dB, require significantpower due to the low thermo-optic coefficient of silica, have problemswith thermal cross-talk between the different optical channels and havea sinusoidal rather than a digital optical response. They also losetheir switching state when power is lost.

What is needed is a Silicon-On-Insulator (SOI) platform formonolithically integrating optical, mechanical and electrical functions.The use of a silicon platform enables fabrication of components usingthe vast infrastructure and process development available forsemiconductor IC manufacturing at silicon foundries. By fabricating theMEMS switches and waveguides in the same material, single crystalsilicon, there are no stress and strain issues as exist withheterogeneous materials sets such as silica-on-silicon. Fabrication insilicon also allows for integration with CMOS microelectronics forcontrol and sensing capabilities, and for free-carrier plasma dispersioneffects to enable signal leveling using integrated VOA's. The high indexcontrast of silicon (n=3.5) enables the ridge waveguide structures tomake tight turns with minimum optical bending loss, decreasing overallchip size to centimeter dimensions.

SUMMARY

An optical micro-electro-mechanical system (MEMS) switch is disclosed.In a preferred embodiment the optical MEMS switch is used as an M×Noptical signal switching system. The optical MEMS switch comprises aplurality of optical waveguides formed on a flexible cantilever beamplatform for switching optical states wherein the state of the opticalswitch is changed by a system of drive and latch actuators. The opticalMEMS device utilizes a latching mechanism in association with a thermaldrive actuator for aligning the cantilever beam platform. In use theoptical MEMS device may be integrated with other optical components toform planar light circuits (PLCs). When switches and PLCs are integratedtogether on a silicon chip, compact higher functionality devices, suchas Reconfigurable Optical Add-Drop Multiplexers (ROADMs), may befabricated.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are not to scale and are only for purposes of illustration.

FIG. 1 is a cut away top plane view of an optical MEMS (Micro ElectroMechanical System) switch in accordance with the present invention;

FIG. 2 is an enlarged view of a portion of FIG. 1 for illustrativepurposes;

FIG. 3 is a side cross-sectional view of FIG. 2;

FIG. 4 is a graphically view of a timing diagram for controlling a latchand drive switch shown in FIGS. 1 and 2;

FIG. 5 is a top plane view showing the latch actuated to an openposition;

FIG. 6 is a top plane view showing the drive switch actuated to anovershoot position;

FIG. 7 is a top plane view showing the latching mechanism in the latchedposition;

FIG. 8 is a cut away top plane view of an optical MEMS device with a“hook” hitch and latch teeth in accordance with another embodiment ofthe present invention;

FIG. 9A is an enlarged view of a portion of FIG. 8 detailing the “hook”hitch in an equilibrium state;

FIG. 9B is an enlarged view of a portion of FIG. 8 detailing the latchteeth in an equilibrium state;

FIG. 10A is an enlarged view of a portion of FIG. 8 detailing the “hook”hitch in a first switch state;

FIG. 10B is an enlarged view of a portion of FIG. 8 detailing the latchteeth in a first switch state;

FIG. 11A is an enlarged view of a portion of FIG. 8 detailing the “hook”hitch in a second switch state; and

FIG. 11B is an enlarged view of a portion of FIG. 8 detailing the latchteeth in a second switch state.

DETAILED DESCRIPTION

Referring now to FIG. 1 there is shown a top plane view of an opticalMEMS (Micro Electro Mechanical System) switch 10. All optical and movingmechanical components shown are fabricated in the single-crystal silicondevice layer of a SOI wafer using a self-aligned process. The opticalMEMS switch 10 utilizes a latching mechanism 20 in association with athermal drive actuator 30 for aligning a flexible cantilever beamplatform 50 fixed at one end 58. The flexible cantilever beam definesone or more movable waveguides for switching to one or more stationarywaveguides defined on an optical slab 40. The components fabricated inthe device layer of an SOI wafer may be released by sacrificial etchingof the buried oxide layer. In use the optical MEMS switch 10 may beintegrated with planar light circuits (PLCs). When switches and PLCs areintegrated together on a silicon chip higher functionality devices, suchas Reconfigurable Optical Add-Drop Multiplexers (R-OADM), may befabricated.

As shown in FIGS. 1 through 3, the optical switch 10 comprises one ormore thermal drive actuators 30 having associated during fabrication oneor more thermal latch actuators 21, each thermal latch actuator 21supports translating latch teeth 22. The flexible cantilever beamplatform 50 defines a plurality of optical waveguides 52 and 54. Atether 34 connects the one or more thermal drive actuators 30 to theflexible cantilever beam platform 50. A linkage 28 connects the thermaldrive actuators 30 to a set of linkage teeth 24 wherein the linkageteeth 24 are contacted by the latch teeth 22 when the latch is engaged.The linkage teeth 24 and latch teeth 22 are spatially located todetermine one or more latched state positions wherein electrical stimuliis timed to actuate the thermal drive 30 and thermal latch actuators 21so as to switch between equilibrium and latched states as will be morefully described below.

The optical MEMS switch 10 is applicable as an optical switch in avariety of applications, such as optical fiber transmission networks, toroute optical signals along various signal paths. Switches are typicallycharacterized by the number of input and output ports, referred to asM×N. For example, a 1×3 switch would switch one input between threeoutputs. M×N switches have previously been implemented using waveguideshuttles or by cascading a series of M 1×N cantilever switches. Whileshuttle switches can provide the M×N switching functionality, theyrequire at least two gaps in the optical pathway, which leads toincreased optical losses. Similarly, a series of M cascaded cantileverswitches would have M optical gaps which leads to increased opticallosses for M>1. By fabricating an M×N cantilever beam waveguide switch,where a cantilever beam carrying M waveguides is deflected rather than awaveguide shuttle, only one optical gap is required in the opticalpathway, cutting the optical loss associated with propagation throughthe gaps in half. Alternatively M cantilever beams, each carrying asingle waveguide, can be flexibly connected so that they all actuatetogether. Furthermore, reflections from the two gaps associated with ashuttle can cause additional losses due to interference.

Turning once again to FIGS. 1 through 5 there is shown the opticalswitch 10 with two optical waveguides 52 and 54 formed on the flexiblecantilever beam platform 50 for switching between two stationary opticalwaveguides 42 and 44, respectively. This configuration enables twooptical signals to be switched at the same time. By including additionaloptical waveguides, additional signals may be switched simultaneously.The ability to switch multiple signals at the same time is important inmany optical applications. For example, in an R-OADM (ReconfigurableOptical Add/Drop Multiplexer), when an input signal is dropped, a newsignal can be added to the output. Since the add/drop function alwaysoccurs simultaneously, it is possible to decrease the number of requiredoptical switches by implementing a single cantilever switch thatperforms the add drop function on both the input signal, sending it tothe drop line, and the add signal, sending it to the switch's output.Referring to FIG. 3, the optical multiple state latching switch 10 usesoxide anchors 56 to attach components to the substrate 60. As well knownin the art, polysilicon anchors can be utilized instead of oxide.Polysilicon can also be used to fabricate dimples, as commonly practicedin MEMS to avoid stiction.

Referring now to FIG. 4 there is graphically illustrated the timingsequence of the signals used to actuate the drive and latch mechanismsfor the 2×2 switch illustrated in FIG. 1, where the voltages are labeledin FIG. 4 assuming the potential of the handle wafer or base substrate60 is zero. The first portion of the timing diagram shows the latchingsequence. The first step in the latching sequence is to apply a voltage+V1 to one end 26 of each latch actuator 21, and a voltage −V1 to theother end 45 of each latch actuator 21. The voltages on the latchactuators induce ohmic heating in the actuator beams, causing thermalexpansion and the subsequent opening (direction 27) of the latch asshown in FIG. 5. While the latch actuator voltage is still applied, thedrive actuator 30 is stimulated with a voltage +V2 at one end 31 and avoltage −V2 at the other end 33.

FIG. 6 shows how the resulting thermal expansion of the drive actuator30 is sufficient to move the flexible cantilever beam platform 50 andlinkage 28 far enough to the right for the linkage teeth 24 to be wellto the right side of the latch teeth 22. Next the latch actuatorvoltages return to zero, and the latch closes. To finish the latchingsequence, the drive actuator voltages return to zero. As the driveactuator cools, the linkage teeth 24 are drawn in tension (direction 37)against the latch teeth 22 which holds the switch in the desired latchedposition as shown in FIG. 7. To return the switch to its original state,the same sequence of voltages are applied in the reverse timing, asshown in the unlatch portion of FIG. 4. Unlike switches with no latchingcapability, the optical MEMS latching switch 10 only consumes powerduring a change of state, and preserves its state, even if power isinterrupted.

It should be noted that, although the timing diagram shown in FIG. 4depicts square wave voltage pulses, this depiction is meant to beillustrative only of the basic timing, and does not preclude the use ofother waveforms. Furthermore, the voltages applied to the thermalactuators need not be symmetric about zero. However, the use of equalbut opposite polarity pulses, as described above, results in a constantzero voltage at the center of each actuator throughout the latch andunlatch cycle, which reduces electrostatic forces between the actuatorsand the handle wafer 60.

A logic table for the 2×2 switching function is as follows:

State One: Add/Drop function, as shown in FIG. 5

The left movable waveguide 52 (input) is optically aligned to the leftstationary waveguide 42 (drop).

The right movable waveguide 54 (add) is optically aligned to the rightstationary waveguide 44 (output).

State Two: Pass function, as shown in FIG. 7

The left movable waveguide 52 (input) is optically aligned to the rightstationary waveguide 44 (output).

In order to change from state one to state two, a force F can be appliedby a thermal drive actuator 30. In order to deflect the free end by adistance δx, a force F must be applied where F is given by:F=(Ea ³ b/4L ³)δx

Where E is Young's modulus (E=1.65×10⁵ μN/μm² for single crystalsilicon), a is the thinner cross-sectional dimension of the beam 21, bis the thicker cross-sectional dimension of the beam and L is the lengthof the beam. For example, a 1000 μm long beam that is 5 μm thick and 20μm wide would require a force of 13.2 μN to deflect the free end by 8μm, which is sufficient deflection to switch a cantilever beam with two4 μm waveguides.

The switching force F can be applied to the free end of the cantileverbeam 50, or at an intermediate location, or locations as required. Theswitch can also be actuated in the opposite direction by applying aforce F from the thermal drive actuator 30 in the opposite direction. Insome cases it may be preferable to not use the equilibrium position ofthe cantilever beam, since these do not have a strong restoring forcethat returns them to this position since the cantilever beam may bequite long and flexible. Instead only deflected positions may bedesirable to use. In addition, it may be advantageous to angle thereceiving waveguides to better match the direction of propagation of thelight leaving the deflected cantilever beam.

Since the cantilever beam carrying multiple waveguides could be widerthan it is thick, it could suffer undesirable out of plane deflectionssince it is less stiff out of plane than it is in plane, as predicted bythe formulaK=(Ea/4)(b/L)³

As an example for a beam that is 5 μm thick and 20 μm wide, the ratio ofthe stiffness in the horizontal direction of the vertical direction is(20/5)². The beam is 16 times stiffer in the horizontal directionrelative to the vertical direction.

In order to avoid out of plane deflections the appropriate locationalong the cantilever beam 50 may be attached to a switch tether 34 so asto minimize these out of plane deflections. The beam's width may also bedecreased at certain points to decrease its stiffness in the horizontaldirection (e.g. serrated). Joints can be added to make the beam moreflexible in the horizontal direction. The beam can be deflectedbi-directionally to decrease the magnitude of the required deflection.The beam can be thickened or stiffened to make it less flexible in theout-of-plane direction (e.g. by making the beam thicker or by addingsuper structures such as additional beams).

The switches and the waveguides are made together on a single crystalsilicon wafer using widely available semiconductor processing equipment.Such on-chip integration avoids the complex alignment issues associatedwith manually connecting different and larger components with opticalfibers, and avoids the cost and space associated with manufacturing,assembling and packaging the separate components of optical switches.On-chip integration with other components can drive down the cost ofmanufacturing switches and installation of these complicated devices bya factor of ten or more. Currently, these components cost over $1,000per channel.

FIGS. 8 through 11 shows two extensions 100 of the system embodimentdepicted in FIG. 1. The first extension is to a higher order ofswitching, from 2×2 in FIG. 1 to 2×3 in FIG. 8. The second option shownin FIG. 9A is the introduction of a “hook”-hitch 132 and 134 instead ofa simple tether. These two extensions are discussed below.

To increase the system from a 2×2 switch to a 2×3 switch, two additionalelements are required. The first is another stationary waveguideplatform defining stationary waveguides 142, 144 and 146 respectively.The second element is an extra pair of teeth 25 on the linkage 28located after the teeth set 24 as shown in FIG. 9B. For the initialstate of the 2×3 switch, the latch teeth are disengaged as shown in FIG.9B. In this position, the right most moveable waveguide 154 is alignedwith the left most stationary waveguide 142 as shown in FIGS. 8 and 9A.Using an actuation sequence similar to the latching phase shown anddescribed in FIG. 4, the switch can be moved to a second state as shownin FIG. 10B. Here the latch teeth 22 defined by the latch actuator 21engage between the pair of teeth 24 and 25 on the linkage 28, and thetwo movable waveguides 152 and 154 are align with the left most pair ofstationary waveguides 142 and 144 respectively, as shown in FIG. 10A. Athird state can be achieved by executing another latching sequence withhigher voltages on the drive. In this state, depicted in FIGS. 11A and11B, the latch teeth 22 engages behind the pair of linkage teeth 24 andthe two moveable waveguides 152 and 154 now align with the right mostpair of stationary waveguides 144 and 146.

The 2×3 switch example discussed above, is one embodiment of the generalability to achieve N×M switching for small values of N and M. Each N×Mconfiguration requires a sufficient number of fixed and movablewaveguides. Further design considerations may be accounted for toachieve the desired set of switch positions. These include the initialrelative alignment and spacing of the moveable and stationarywaveguides, as well as, the number and relative location of the linkageteeth.

The second option shown in FIGS. 8 through 11 is the substitution of aninterlocking “hook” hitch 132 and 134 for the tether 34. Depending onthe embodiment and fabrication processes employed, the “hook” hitch maybe used to mitigate the affects of stresses that may degrade the switchperformance. For example, if the process were to induce stress in thedrive actuator 30, the stress could be transferred through a tether 34,and impact the equilibrium state alignment of the waveguides. The “hook”hitch mechanically decouples the drive actuator 130 from the moveablewaveguide platform 150 in the equilibrium state, thereby eliminating anytransferred stress that would induce a misalignment in the equilibriumstate.

The “hook” hitch also mitigates stresses that occur in latched statesthat lead to undesirable rotations in the linkage. As the unanchored endof the cantilevered waveguide platform is pulled to the right, thetranslational motion of the platform is accompanied by a small clockwiserotation due to the bending of the cantilevered platform. If a simpletether is used, the rotation of the waveguide platform bends the tether34, which in turn causes a counter clockwise rotation of the linkage 28,and may also asymmetrically distort the drive actuator. The rotation ofthe linkage and asymmetric distortion of the actuator is most severe insystems that require larger displacements. The “hook” hitch, however,provides a good counter measure for these issues. As seen in FIG. 11Athe “hook” hitch combination 132 and 134 provides a pivot point at thecontact point between the left hook 134 attached to the cantileveredwaveguide beam platform and the right hook 132 attached to the thermaldrive actuator. The “hook” hitch thereby decouples the rotational motionof the cantilevered waveguides from the rest of the system, allowing thelinkage and drive to operate without induced rotations.

The invention may be embodied in other specific forms without departingfrom its spirit or essential characteristics. The described embodimentsare to be considered in all respect only as illustrative and notrestrictive. The scope of the invention is, therefore, indicated by theappended claims, rather than by the foregoing description. All changeswhich come within the meaning and range of equivalency of the claims areto be embraced within their scope.

1. An optical multiple state latching switch, comprising: one or moredrive actuators; one or more latch actuators with associated latchteeth; a flexible cantilever beam platform defining a plurality ofoptical waveguides; a tether connecting said one or more drive actuatorsand said flexible cantilever beam platform; a linkage defining one ormore linkage teeth connecting to said one or more drive actuatorslocated for engaging said associated latch teeth located to determineone or more latched state positions; and electrical stimuli timed toactuate said one or more drive and latch actuators so as to changebetween equilibrium and latched states.
 2. The optical multiple statelatching switch according to claim 1, wherein said flexible cantileverbeam platform is pulled or pushed by said one or more drive actuators.3. The optical multiple state latching switch according to claim 1,wherein said flexible cantilever beam platform can be deflectedbi-directionally.
 4. The optical multiple state latching switchaccording to claim 1, wherein said flexible cantilever beam platform hasmechanical features to increase or reduce the stiffness of said flexiblecantilever beam platform.
 5. The optical multiple state latching switchaccording to claim 1, wherein said latching switch is fabricated in thedevice layer of an SOI wafer.
 6. The optical multiple state latchingswitch according to claim 1, wherein said latching switch is fabricatedin the device layer of an SOI wafer and released by sacrificial etchingof the buried oxide layer.
 7. The optical multiple state latching switchaccording to claim 1, wherein said electrical stimuli to said one ormore drive actuators are biased to reduce electrostatic forces acting onsaid actuator.
 8. The optical multiple state latching switch accordingto claim 1, wherein said electrical stimuli to said actuators are biasedto reduce or eliminate voltage differences between contacting surfaceson said latch teeth and said linkage teeth.
 9. An optical multiple statelatching switch, comprising: one or more drive actuators; one or morelatch actuators defining associated latch teeth; a flexible cantileverbeam platform with associated plurality of optical waveguides; ahook-hitch for engaging said drive actuator and said flexible cantileverplatform; a linkage connecting said drive actuator to translatinglinkage teeth located to determine one or more latched state positions;and electrical stimuli timed to actuate said one or more drive and latchactuators so as to change between equilibrium and latched states. 10.The optical multiple state latching switch according to claim 9, whereinsaid flexible cantilever beam platform is pulled or pushed by said driveactuators.
 11. The optical multiple state latching switch according toclaim 9, wherein said flexible cantilever beam platform can be deflectedbi-directionally.
 12. The optical multiple state latching switchaccording to claim 9, wherein said flexible cantilever beam platform hasmechanical features to increase or reduce the stiffness of said flexiblecantilever beam platform.
 13. The optical multiple state latching switchaccording to claim 9, wherein said latching switch is fabricated in thedevice layer of an SOI wafer.
 14. The optical multiple state latchingswitch according to claim 9, wherein said latching switch is fabricatedin the device layer of an SOI wafer and released by sacrificial etchingof the buried oxide layer.
 15. An optical multiple state latchingswitch, comprising: one or more drive actuators; one or more latchactuators with associated latch teeth; a flexible cantilever beamplatform with associated optical waveguides; a hitch for engaging saiddrive actuators and said flexible cantilever beam platform defininglinkage teeth; a linkage defining one or more linkage teeth connectingto said one or more drive actuators located for engaging said associatedlatch teeth located to determine one or more latched state positions;and electrical stimuli timed to actuate said drive and latch actuatorsso as to change between equilibrium and latched states wherein saidelectrical stimuli to said actuators are biased to reduce or eliminatevoltage differences between contacting surfaces on said latch teeth andsaid linkage teeth.
 16. The optical multiple state latching switchaccording to claim 15, wherein said flexible cantilever beam platformhas mechanical features to increase or reduce the stiffness of saidflexible cantilever platform.
 17. The optical multiple state latchingswitch according to claim 15, wherein said flexible cantilever beamplatform has mechanical features to increase or reduce the stiffness ofsaid flexible cantilever platform.